Designation D5902 − 05 (Reapproved 2015) Standard Test Method for Rubber—Determination of Residual Unsaturation in Hydrogenated Nitrile Rubber (HNBR) by Iodine Value1 This standard is issued under the[.]
Trang 1Designation: D5902−05 (Reapproved 2015)
Standard Test Method for
Rubber—Determination of Residual Unsaturation in
This standard is issued under the fixed designation D5902; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision A number in parentheses indicates the year of last reapproval A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1 Scope
1.1 This test method covers the Wiijs procedure for the
determination of unsaturation (iodine value) in hydrogenated
nitrile rubbers
1.2 This test method is applicable only to those
hydroge-nated nitrile rubbers derived from copolymers of acrylonitrile
and butadiene
1.3 Iodine values are reported in centigrams of iodine per
gram of HNBR [cg(I2)/g] Higher iodine values indicate higher
levels of unsaturation
1.4 This test method is appropriate for calculating the
percent residual unsaturation of hydrogenated nitrile rubber if
the iodine value of the base polymer before hydrogenation has
been determined
1.5 The values stated in SI units are to be regarded as
standard No other units of measurement are included in this
standard
1.6 This standard does not purport to address all of the
safety concerns, if any, associated with its use It is the
responsibility of the user of this standard to establish
appro-priate safety and health practices and determine the
applica-bility of regulatory limitations prior to use.
2 Referenced Documents
2.1 ASTM Standards:2
D1193Specification for Reagent Water
D1959Test Method for Iodine Value of Drying Oils and
Fatty Acids(Withdrawn 2006)3
D4483Practice for Evaluating Precision for Test Method
Standards in the Rubber and Carbon Black Manufacturing
Industries
3 Summary of Test Method
3.1 A sample of the raw, unvulcanized rubber is dissolved in chloroform
3.2 The dissolved sample is reacted with Wiijs solution 3.3 When the reaction is completed, potassium iodide solu-tion is added
3.4 The resultant solution is then back-titrated with sodium thiosulfate solution and the iodine value is calculated
4 Significance and Use
4.1 Hydrogenated nitrile rubbers are available at different levels of unsaturation and different acrylonitrile content Highly saturated grades offer optimum resistance to aging, such as exposure to heat, ozone and chemicals, and can be cured effectively only with peroxides or high energy radiation 4.2 Partially unsaturated grades can be cured by sulfur systems in addition to peroxides and high energy radiation 4.3 This test method provides a technique to determine the unsaturation level of hydrogenated nitrile rubbers in the raw, unvulcanized state It can be used for research and development, quality control, and referee purposes
5 Apparatus
5.1 Erlenmeyer Flasks, with ground glass stoppers (300
mL)
5.2 Flask Shaker.
5.3 Pipets.
5.4 Constant Temperature Bath.
6 Reagents
6.1 Reagent grade chemicals shall be used in all tests All reagents shall conform to the specifications of the Committee
on Analytical Reagents of the American Chemical Society.4
1 This test method is under the jurisdiction of ASTM Committee D11 on Rubber
and is the direct responsibility of Subcommittee D11.11 on Chemical Analysis.
Current edition approved June 1, 2015 Published September 2015 Originally
approved in 1996 Last previous edition approved in 2010 as D5902 – 05 (2010).
DOI: 10.1520/D5902-05R15.
2 For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.
3 The last approved version of this historical standard is referenced on
www.astm.org.
4Reagent Chemicals, American Chemical Society Specifications, American
Chemical Society, Washington, DC For Suggestions on the testing of reagents not
listed by the American Chemical Society, see Annual Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia and National Formulary, U.S Pharmacopeial Convention, Inc (USPC), Rockville,
MD.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959 United States
Trang 2Other grades may be used, provided it is first ascertained that
the reagent is of sufficiently high purity to permit its use
without lessening the accuracy of the determination
6.2 Purity of Water—Unless otherwise indicated, references
to water shall be understood to mean reagent water conforming
to Type I of SpecificationD1193
6.3 Chloroform.
6.4 Wiijs Solution (prepared in accordance with Test Method
D1959)
6.5 Potassium Iodide Solution (prepared in accordance with
Test Method D1959)
6.6 0.1 N Sodium Thiosulfate Solution (prepared in
accor-dance with Test Method D1959)
6.7 Starch Indicator Solution (prepared in accordance with
Test Method D1959)
7 Procedure
7.1 If the approximate level of unsaturation is known, the
following sample sizes are recommended:
Approximate unsaturation level Sample weight in mg
If the approximate level of unsaturation is unknown, a
sample weight of 680–720 mg is recommended
7.2 Weigh the finely divided sample to the nearest 0.1 mg
Add the sample to a 300-mL glass stoppered Erlenmeyer flask
containing 50 mL of chloroform Using the flask shaker, shake
until the samples are completely dissolved in the chloroform
(approximately 1 h)
7.3 Immediately place the flask containing the dissolved
sample into a constant temperature bath maintained at 23 6 1
°C for 30 min
7.4 Pipet 25 cm3of Wiijs solution into the flask containing
the specimen while shaking the flask Replace the glass stopper
and return the flask to the constant temperature bath maintained
at 23 6 1 °C for 2 h
7.5 Remove the flask from the constant temperature bath
and quickly add 10 cm3 of potassium iodide solution while
shaking the flask vigorously
7.6 Wash off any iodine from the stopper into the flask with
distilled water Wait 5 min before beginning the titration
7.7 Titrate with the 0.1 N sodium thiosulfate solution,
adding it gradually while shaking the flask vigorously
Con-tinue the titration until the yellow coloring is just about to
disappear Add 1 to 2 cm3 of starch indicator solution and
continue the titration until the violet color just disappears
7.8 Allow the flask to stand for 30 min after the titration,
then shake the flask, and if color returns, continue the titration
7.9 Run a blank determination following the titration steps
as described in 7.2through7.8concurrently with the sample
under test
8 Calculation
8.1 Calculate the iodine value as follows:
Iodine value 50.1 3 f 3~B 2 A!3 126.9 3 100
50.1 3 f 3~B 2 A!3 12.69
M
where:
f = normality factor of the 0.1 N sodium thiosulfate
solution,
A = cm3 of sodium thiosulfate solution required for
titration of the sample,
B = cm3 of sodium thiosulfate solution required for
titration of the blank,
M = mass of the sample in grams,
1000 = conversion factor from the mg equivalent of
so-dium thiosulfate to the g equivalent, and
100 = conversion factor from g to cg
8.2 Calculate the percent of residual unsaturation if the iodine value of the base polymer prior to hydrogenation is known, as follows:
Iodine value of the base polymer3100
9 Report
9.1 The report shall include the following information: 9.1.1 Proper sample identification,
9.1.2 Number of data points used to obtain the result, 9.1.3 The iodine value obtained, and
9.1.4 The percent of residual unsaturation to the nearest 0.1 %, if applicable
10 Precision and Bias 5
10.1 This precision and bias section has been prepared in accordance with PracticeD4483 Refer to PracticeD4483for terminology and other statistical calculation details
10.2 Precision—The precision results in this precision and
bias section give an estimate of the precision of this test method with the materials (rubbers) used in the particular interlaboratory program as described in 10.3 and 10.4 The precision parameters should not be used for acceptance/ rejection testing of any group of materials without documen-tation that they are applicable to those particular materials and the specific testing protocols that include this test method 10.3 A Type I/Class II interlaboratory precision was evalu-ated Both repeatability and reproducibility are short term A period of one week separates replicate test results Each determination (measurement) is a test result
10.4 Three different materials (grades of hydrogenated ni-trile rubber) with different degrees of unsaturation were used in
5 Supporting data have been filed at ASTM International Headquarters and may
be obtained by requesting Research Report RR: D11-1078.
Trang 3the interlaboratory program These materials were tested in
four laboratories on two different days one week apart
Duplicate tests were run on each day The analysis for precision
followed the general procedure as set forth in Annex of
Practice D4483 Each cell of Table A5.1 in Practice D4483
contained four values (two test days, two results each day) The
estimates for repeatability parameters contain two
undifferen-tiated sources of variation, replicates within days and between
days The final precision parameters are given in Table 1
10.5 The precision of this test method may be expressed in
the format of the following statements that use what is called
an “appropriate value” of r, R, (r) or (R), that is, that value
obtained fromTable 1to be used in decisions about test results
of this test method
10.6 Repeatability—The repeatability of this test method
has been established as the appropriate value for any parameter
as tabulated inTable 1 Two single test results obtained in the
same laboratory, under normal test method procedures, that
differ by more than this tabulated r must be considered as
derived from different or nonidentical sample populations
10.7 Reproducibility, R, of this test method has been
estab-lished as the appropriate value for any parameter as tabulated
in Table 1 Two single test results obtained in two different laboratories, under normal test method procedures, that differ
by more than this tabulated R must be considered as derived
from different or nonidentical sample populations
10.8 Repeatability and reproducibility expressed as a
per-centage of the mean level (r) and (R) have equivalent
applica-tion statements as10.6and10.7for r and R For the (r) and (R)
statements the difference in the two single test results is expressed as a percentage of the arithmetic mean of the two test results
10.9 Bias—In test method terminology, bias is the difference
between an average test value and the reference (or true) test property value Reference values do not exist for this test method since the value (of the test property) is exclusively defined by the test method Bias, therefore, cannot be deter-mined
11 Keywords
11.1 HNBR; iodine value; residual unsaturation
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TABLE 1 Type 1 Precision
Residual Unsaturation of HNBR by Iodine Value HNBR Nominal
Content
ACN,
%
Mean (cgI 2 /g)
Within LaboratoryA
Between LaboratoryA
ASymbols are defined as follows:
S r= within-laboratory standard deviation,
r = repeatability, measurement units,
(r) = repeatability, %
S R= between-laboratory standard deviation,
R = reproducibility, measurement units, and
(R) = reproducibility,%